According to National Renewable Energy Laboratory, heating and air conditioning are two of the primary reasons for operating the main engine in a long-haul truck during the driver rest period. Argonne National Laboratory calculated that in the United States, long-haul trucks (those that travel more than 500 miles per day) use 838 million gallons of fuel annually for rest period idling to provide electric energy for air-conditioning (A/C) or heating. Many states in the US have adopted anti-idling regulations to force improved fuel economy and reduced GHG emissions by prohibiting idling of the engine for extended periods of time.
However, the anti-idling regulations, together with regulations requiring regular breaks, pose a challenge to maintain cabin comfort during road-side, truck stop, or parking lot rest period for the drivers who sleep in the sleeper cabin. Alternative thermal comfort maintenance solutions are desired to provide rest period cabin comfort without idling the engine to drive the HVAC system.
Several technical solutions have been investigated to provide cabin comfort. Those include various types of Auxiliary Power Units (APU), fuel fired heaters, Adsorption A/C and Heat Pump Systems, etc., with varying degrees of success. The mainstream solution of today is to use an enlarged-capacity battery pack to provide the required electric power to drive an A/C system or electric heater for year-round comfort.